Central hemodynamic effects of recombinant human relaxin in the isolated, perfused rat heart model

To determine the cardiac effects of relaxin in the isolated, perfused rat heart model, and to see if pregnancy modifies the hormone's actions. Hearts were excised from 18 female Sprague-Dawley rats (ten pregnant, eight nonpregnant) and attached to a Langendorff apparatus. Left ventricular systolic pressure, heart rate, and contractility were measured. Hearts were exposed serially to 0.5,1.0, 2.0, 4.0, 8.0, and 16.0 ng/mL concentrations of recombinant human relaxin. Hearts from pregnant rats had lower heart rates than those from nonpregnant animals. Relaxin increased heart rate, left ventricular systolic pressure, and contractility in a dose-dependent fashion. Pregnancy did not modify this response. Recombinant human relaxin is a potent inotropic and chronotropic agent. The effects coupled with the physiologic increase of relaxin during human pregnancy indicate that relaxin may be involved in the cardiovascular changes of pregnancy.